It has been intensively developed a product of testing or processing system utilizing laser in fields of bio cell analysis and processing. Flow cytometry may be listed as one example. Flow cytometry is a technique of dispersing cells in living bodies in fluid, of flowing the fluid as a narrow flow and of optically analyzing the individual cells. A system for use in flow cytometry is called flow cytometers.
A flow cytometer irradiates laser light onto cells, and then detects forward scatter (abbreviated as FSC) in a direction slightly shifted from the rays (it would be saturated with strong light from a light source on the same axis as the light) and side scatter (SSC) in a direction perpendicular to the light. Further, the cells are labeled with a fluorescence material and fluorescence generated by the laser light is detected. In the case of cells, the size of the cells can be analyzed by FSC and the complexity within the cells (derived from shape of the nuclei, organelles, film structure or the like) can be analyzed by SSC. Thanks to combination of detectors, fluorescence materials and immunostaining, various kinds of analysis can be made. It has recently supplied a system utilizing a plurality of lights and detectors (4 kinds of lights, 14 kinds of detectors or the like), and a plurality of antibodies may be used to perform more sophisticated analysis at the same time. It has been further supplied a system including a cell sorter as a standard equipment, so that target particles can be taken at a high precision and high speed by switching flow routes in a sheath. Maximum of 4 kinds of populations can be separated out using a commercial system, and it is possible, in theory, to process 90000 particles per one second.
As a laser, it has been used a large gas laser of water cooled type requiring complicated operation in prior arts. Thanks to development of laser technology and a flow cell detection system of high sensitivity, it is mainly used air cooled type laser which is compact, simple and has a long life. It has been specifically used air cooled type argon laser (488 nm), air cooled type helium-neon laser (633 nm), air cooled type helium-cadmium laser (325 nm) or the like. More recently, it has been used a semiconductor laser or a solid state laser (light-excited semiconductor laser), utilizing a wavelength conversion device, which are more compact and consume a less electric power.
According to flow cytometers, laser light may be transmitted through an optical fiber until it is irradiated into fluid. The optical intensities of the used laser may exceed several tens to a hundred mW, so that a total of the intensities at all the wavelengths may be 300 mW or higher. Further, the spot size is as large as several tens μm or more, so that it is used a multi-mode fiber of several tens μm or larger as the optical fiber. In this case, it is required that the spot shape of the laser light is stable and not deviated for accurately measuring the individual cells. Therefore, for stabilizing the spot shape or optical intensity of the laser light, it may be used an optical regulation device for modulating the intensity or phase.
As an optical modulation device utilizing a ridge type optical waveguide, Japanese Patent Publication Nos. 2002-250949A, 2005-221894A and S63-049732A were flied, for example.
According an optical modulation device in Japanese Patent Publication No. 2002-250949A, a ridge type optical waveguide is adhered to a supporting body.
An optical modulation device according to Japanese Patent Publication No. 2005-221894A is made of a material exhibiting secondary non-linear optical effects. It is further included a first step of adhering a first substrate 21 having a periodic domain inversion structure and a second substrate 22 by diffusion adhesion through thermal treatment, a second step of polishing the first substrate 21 into a predetermined thickness for forming the optical waveguide therein, and a third step of adhering the first substrate 21 to a third substrate 23 by diffusion adhesion through thermal treatment. Further, as the ridge type waveguide, it is disclosed the structure of grinding parts of the first, second and third substrates.
According to an optical modulation device described in Japanese Patent Publication No. S63-049732A, a ridge type optical waveguide is formed on an x-cut LN substrate, belonging to an electro-optic material, and electrodes are formed on the side faces.
Besides, as a measure against drift of an optical modulator, it is described to use an SiO2 buffer layer in Japanese Patent No. 1789177B.